Based on observations collected at the European Southern Observatory, Chile in program 75.C-0851(C), 76.C-0847(A), 77.C-0831(A+D).

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Simbad names: [NC98] Cha HA 1, [NC98] Cha HA 2, etc.

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... B 34

Simbad name: CHXR 76.

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...2000)

Luhman (2004, 2007) derives systematically higher effective temperatures and luminosities for the objects leading to higher mass estimates when compared with evolutionary tracks, e.g. 0.1 $M_{\odot }$ for Cha H $\alpha$ 8 instead of 0.07 $M_{\odot }$ .

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...2006)

The four objects classified as spectroscopic binaries in the survey by Kurosawa et al. (2006) display very small RV differences (0.2-0.5 km s^-1). It has to be further investigated whether it can be excluded that they are caused by systematic errors. If interpreted as RV semi-amplitudes caused by companions at $\leq$ 0.1 AU, these companions would have masses $M_2 \sin i$ in the planetary regime (1-2 $M_{\rm Jup}$ ) (see Sect.3). In both cases, systematic errors or planets, we would not count them as binaries yielding a binary fraction of this survey of $\leq$ $6\%$ (0/17).

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